Rheostat



. G. KJELLGREN.

RHEOSTAT.

APPLICATION FILED NOV. 13, 1919.

Patented Jan. 17, 1922.

. ANA

' J. G. KJELLGREN.

RHEOSTAT.

APPLlCATl'ON FILED NOV. [3, I919.

1,404,125. Patented Jan. 17, 1922.

4 SHEETS-SHEET s.

Patented Jan. 17, 1922.

J. .KJELLGREN.

RHEOSTAT.

APPLICATION FILED NOV. 13. 1919.

Le. KJELLGREN.

RHEOSTAT.

APPLICATION FILED NOV. 13. 1919.

Patented Jan. 17, 1922.

4 SHttlS-SHEET 4- UNITED STATES JOHN PATENT OFFICE.

G. KJ'ELLGREN, OF CLEVELAND, OHIO, ASSIGNOR TO THE ELECTRIC RAILWAYIMPROVEHENT 00., OF CLEVELAND, OHIO, A CORPORATION 01 OHIO.

RHEOSTAT.

To all whom it may concern;

Be it known that I, JOHN G. KJEILGREN, a subject of the King of Sweden,and residing at Cleveland, in the county of Cuyahoga and State of- Ohio,have invented certain new and useful Improvements in Rheostats, of whichthe following is a specification.

My invention relates to rheostats, and particularly to rheostats of thegeneral type shown in my co-pending application Serial No. 140,953,filed January 6, 1917, the object of my invention being to provide asingle and rugged, construction adapted for out of door service, andimproved in certain features hereinafter described or shown in theaccompanying drawings in which- Fig. 1 is a side elevation of a rheostatin which my invention is embodied in one form;

Fig. 2 is a plan thereof;

Fig. 3 is an end elevation'thereof;

Fig. 4 is a transverse section on the line 44 of Fig. 1;

Fig. 5 is a diagram of the wiring'system;

Fig. 6 is an enlarged section through one of the insulated cross barsdrawn to an enlarged scale;

Fig. 7 is a partial section through one of the bus bars and its terminalreceptacle;

Fig. 8 is a horizontal section through a bus bar and its connectionterminal;

Fig. 9 is a transverse section through a bus bar showing the connectionof a resistance coil thereto; and

Fig. 10 is an enlarged side elevation of one of the terminal receptaclesand its door.

In the embodiment of my invention here illustrated, my improved rheostatcomprises a skeleton frame, the angle iron end posts 10 of which areunited on each side by three vertically spaced longitudinal channels 11.Extending between the channels are staggered cross bars 12, which serveas guides and insulating supports for the group of parallel resistancewire coils 13. The latter pass in zigzag arrangement from one end of theframe to the other, being engaged with each cross bar 12 as it passes.The current enters the rheostat through a main switch 14, which may bemounted in any suitable position upon the frame, here shown on the top,and is led by conductors passing through the insulating sheath 15 (Fig.2) to a bus bar 16 arranged at one Specification of Letters Patent.

Patented Jan. 17, 1922.

Application filed November 18, 1919. Serial No. 337,646.

end of the frame. On this bus bar are the terminals 17 of a group ofdistributing switches 18 interposed between certain of the resistancewires and the bus 16. At the opposite end of the frame are several busbars 19 and 20, 21 and 22, spaced longitudinally apart beneath the frameand connected at spaced intervals to the resistance wires. Plugreceptacles 23 associated with the busbars afford convenient means forconnecting the lead (not shown), through which the current is tapped offfrom the rheostat to the point of use. An auxiliary bus bar 24 may bearranged in like position at the switch end of the frameand connected toone of the buses at the opposite end. The bus 22 is here shown connectedto the bus 24. The receptacle 23 for the bus 24 thus affords anauxiliary tapping point of like capacity as that of the bus 22. In thepresent case the full resistance of the rheostat is interposed betweenthe entrance bus 16 and the tap bus 22, so that the latter and the bus24, which is tied to it, take the lowest possible current from therheostat.

When the rheostat is to be used on a track, as for example when it isused in connection with electric welding apparatus for rail bending,itmay be mounted through its corner posts 10 on the axle rods 25. Thelatter are angled up at their inner ends and riveted to the channel 11,while at their outer ends they are laterally extended horizontally toform bearings for the running wheels 26. Any other suitable means may beutilized to expedite the transport of the rheostat from place to place,it being a simple matter, in any type of wheel construction, to securethe supporting wheels to the frame of the rheostat without requiring anadditional frame for the running gear. Preferably there are alsoprovided extensible handle bars 27 of U shape at each end of the frame,by means of which the apparatus may be bodily lifted and carried fromplace to place. In order not to interfere with the track signal circuit,I have here shown the wheels 26 at one end of the frame insulated bybushings 28 1) from the axle rods, while those at the other end serve toground the frame as a matter of precaution and protection for theoperators. Chests or other casings 29 may be mounted at the ends of theframe close necessitate an msulating covering of special character forthe cross bars 12 to which they are attached. To meet this situation,the steel tubin 31 (Fig. 6) which forms the core of eac 'cross bar, isfirst encased in a waterproof the latter, as well as ,to prevent micatube 32 ofhigh insulating capacity." This is protected against heat by awrapping 33 of asbestos tape. To bind and shedding of mica scales, Ithen apply an insulating cement 34.- The resistance wires 13 are thenattached to the cross bars, for example by wrapping the wire around thebars (one full turn at the mid bar, and approximately one and threequarter turns at the top and bottom bars), or bynarrow' clamps on therods, whereupon a further covering 35 of fire-proof, moisture-proofinsulating cement-is applied which embedsthe wire fastening. By passinga heavy current fthrough the rheostat the cement is baked hard and formsa waterproofing dielectric covering which holds all the elements of theinsulating covering together rigidly and prevents deterioration. It isto be borne in mind that thepresent rheostat is designed to operate outof doors, and under practically all weather conditions. Consequently theinsulating problem is quite difficult, particularly when utilizing, asthe resistance element, high temperature resistance wires. Asbestos is agood insulator against both heat and electricity but it is somewhathygroscopic, and will not do for outside work unless protected against 1moisture. Mica is perhaps the best'non-conductor of electricity, butmust be protected against the burning out of the binder which holds themica scales in place. The present construction is one which is not onlymechanically strong,-but afi'ords excellent insulation Q under the mosttrying conditions.

When the voltage to be controlled is not very high,,the insulated crossbars may be mounted directly in the channels 11. But when the voltage ishigh, I prefer to make the holes'in the channels sufliciently large tospace the same from the cross bars which pass therethrough. 'In suchcases strips of heavy insulation 36 are secured in the bottoms of thechannels and are pierced to receive and'closely engage the ends of thecross bars. The latter are thus mounted'i'n an insulating support ofsufiicient mechanical strength.

The distributing switches 18 are mounted on a common insulating base 37backed by a sheet of asbestos 38, for heat protection. Air spaced from'the'latter is a screen 39 of asbestos board, which still furtherprotects the switches from the heat of the" rheostat as well asaffording a channel for air cooling. As explained in my applicationabove mentioned, the resistance coils are of high temperature,non-corrosive wire and are operated at exceedingly high temperatures, sothat protection of the switch against their radiant heat is a practicalnecessity. The distribution of the current by the switches may be variedas desired. Some of the wires are connected ,to the entrance bus bar 16,others through the switches. If preferred all may be connected throughthe switches, and in such case one switch may control a group of wires.By the use of distributing switches of this character, and a group ofconnection bus bars, to any one of which the working lead may be shiftedto compensate a drop in the line voltage, a practically constant currentmay be maintained at the operating tool. I

. The receptacles 23 (Fig, 7) for the connectingblock of the lead areshown located 'below the bottom longitudinal channel 11, although theymay be placed elsewhere if desired. The jack contact 40 is formed from abrass rod slotted at one end to receive the bus bar to which it isriveted at 41. The

jack end of the rod is counterbored at 42 and slotted to form springfingers 43, which insure a good wiping contact with the plug of the leadwire. These jacks, which are arranged at each end of each bus bar, passthrough insulating materialwhich serves to separate both the jack rodsand the bus bar. For insulation I preferto use a block 44 ofmechanically strong material, such as formlca fiber and protectedagainst heat ,by a block 45 of asbestos material which is relat1velyweak mechanically. A casing 46 surrounding the jack, but separatedtherefrom by aninsulating bushing 47, is provided to prevent accidentalcontact with the jack. To afi'ord additional support for the insulations44 and-45 I provide a light angle iron 48 at the lower margin of theinsulating blocks, which is attached to the corner angle 10 at one endand supported at its other end by a downward extension of the trussstrap 49 (Fig. 1) of the frame.

The manner in which the resistance wires are connected to the bus barsmay be variously modified, but I have shown a simple construction inFig. 9. The bar is pierced adjacent'its upper edge to receive a seriesof clamping bolts 50, and the wire is looped beneath the head of thebolt on one side of the bar, carried over the top of the latter, and

' down on the other side, where it is wrapped ping off the current onthe bolt beneath the nut so that on screwing u the latter the wire issecurely clamped in 00d electrical connection to the bar.

0 prevent accidental connection to the rheostat at taps of lowresistance, I provide covers 51 (Fig. 10) over the taps of the busbars19, 20 and 21, but leave exposed the taps for the bus bars 22 and24. While these covers are pivoted and may be raised to obtain access tothe taps for the bars 19, 20 and 21,

the operator is nevertheless warned thereby that he is plugging into arelatively high current and is automatically guided into the open tapsof the bars 22 and 24. This is a feature of considerable practicalvalue, especially in work around mines where unskilled operators arecommon and there is considerable danger of serious injury not only tothe operator, but to the rheostat and the working tool by taking excesscurrent from the rheostat.

It will be noted as a feature of convenience that the main switch 14 maybe operated from both sides of the frame, and that the current tap jacksare arranged at each end of each of the bus bars for the same reason.The screens 52 extending above the frame on opposite sides of the mainentranceswitch protect the latter against mechanical injury, while asheet of asbestos board 53 is provided upon which the switch rests, andby which it is protected from the heat of the rheostat.

The construction illustrated may be varied in detail without departingfrom what I claim as my invention.

I claim 1. A rheostat comprising longitudinally extending side membersof structural metal, strips of mechanically strong insulation carried bysaid side members, and cross bars for its resistance wires, said crossbars passing with clearance through said metal side members and beingsupported in said insulation.

2. A rheostat comprising longitudinal side channels, insulation securedin the bottoms of said channels and cross bars for the resistance wires,said cross bars passing with clearance through said channels and beingsupported in the insulation secured therein.

3, A rheostat comprising an open-work frame, a series of transverseinsulating bars arranged in staggered relation in said frame, a group ofresistance wires supported in zigzag position on said transverse barsand insulated thereby from each other and from said bars, a group of busbars connected to said resistance wires at spaced intervals, and meansassociated with such bus bar for tappassing through the rheostat.

at. A rheostat comprising an open-work frame of generally rectangular,elongated *lating cross bars, a group of resistance wires supported bysaid insulating bars, and insulatedthereby from each other, incombination with a group of bus bars pierced to receive a series ofsecuring screws corresponding. to the series of resistance wires, eachof said wires being secured to said bus bar by an independent securingscrew, and being carried therefrom to a succeeding insulating cross bar,substantially as described.

6. In a rheostat, a bar for supporting the resistance wires, said barcomprising a metal tube, an insulating sheath surrounding the same, andan outer insulating cement of heat-resistance water-proofing material.

7. In a rheostat, a bar for supporting the resistance wires, said barcomprising a metal tube, an insulating sheath surrounding the same, andan outer insulating cement of heat-resistance water-proofing material,the resistance wires being embedded in said cement.

8. In a rheostat, a bar for supporting the 1 resistance wires, said barcomprising a metal tubing with insulating sheath, said sheath having aninner layer of mica, a superposed layer of asbestos, and aheatresistant, moisture-proof outer! cement of 1 insulating material inwhich the wires are embedded.

9. In a rheostat, a group of resistance wires arranged zigzag inparallel, and isolated from each other, switch means for dis- 110tributing the current to the resistance wires, and a group of bus barsconnected at spaced intervals to the resistance wire group, andindependent tap terminals offset from but mechanically and electricallyconnected to 11 said bus bars to facilitate tapping off currenttherefrom.

10. In a rheostat, a frame, a group of resistance wires supportedtherein, switch means arranged at one end of the frame for 120distributing the current to the resistance wires, said switch meanscomprising an insulating base mounted in substantially vertical positionon the frame, and a screen of heatinsulating material spaced from thebase 125 and interposed between the latter and the resistance wires toafford an air cooling channel for the switch base.

11. In a rheostat, a group of tap outlets of different current capacity,and covers for 0 fl I i I i h the outlets of greiiter capacity, theoutlet of euit, while the wheels at the other end of the heat capacitybei hg exposed for unobstruetframe are 'eleetrically connected theretoto 12. In a rheostat; a frame, track rvheels In testimony whereof I havesigned my 5 supported thereon,. the wheel at one end of name tothisspeeification. the frame being insulated therefrom to pre edconnection thereto. ground the same. Y 10' vent interference with a,track signal cir- 1 A JOHN G. KJELLGREN. I

